Prince Akishino and Princess Kiko leave the imperial palace in Tokyo on June 29, 1990, after reporting their marriage to the emperor.

Associated Press

There’s no need to share everything – that’s the key to maintaining a healthy relationship in a marriage, according to one of Japan’s imperial couples.

Prince Akishino and Princess Kiko celebrated their 25th wedding anniversary on Monday with a message that touched on their quarter century together. The note, which takes the form of a one-on-one dialogue between the couple, begins with Prince Akishino reminiscing about how he first spoke with his future wife at a bookstore in May 1985, and how he asked her to marry him the following year.

Prince Akishino and his daughter, Princess Mako, at Tokyo’s Haneda airport in November 2013.

Associated Press

In the memo, Princess Kiko shared how she had difficulties trying to discuss wedding preparations with the prince, who was in the U.K. then. “Back then, we didn’t have e-mail as a common tool of communication and had only phones and faxes,” she said, adding that she was worried preparations wouldn’t end in time for the actual ceremony.

On their children, Prince Akishino wrote that he was delighted to receive a Father’s Day card this year from his daughter, Princess Mako, who is now studying the U.K. “Usually, we only exchange the minimum amount of messages via e-mail, so it made me oddly happy,” the prince said. On the couple’s second daughter, Princess Kako, the prince said that she is often curt towards him but can be surprisingly kind at times.

Princess Kako, the second daughter of Prince Akishino and Princess Kiko, in December 2014.

Associated Press

Regarding their 25 years together, the prince said that they get into arguments every now and then which is common for any couple. “It might be disappointing that I don’t say this often, but I certainly feel gratitude toward you,” the prince said to his wife in the dialogue.

The prince goes on mention that while sharing many experiences together helped the two grow closer, it was crucial that they have different hobbies. “Hobbies should be enjoyed separately” since it’s likely to lead to competition and affect the relationship if they share it, he said.

The couple rated each other as partners and parents on a scale of four, and the prince said that he would give his wife “satisfactory” rating, which is the second lowest. Princess Kako also gave him the same passing score.

“This probably means that we both have a lot of space for improvement. We should continue working toward being rated as excellent or good in the future,” the prince said.

Prince Akishino is second in line to the Chrysanthemum Throne, after Crown Prince Naruhito. Prince Akishino and Princess Kiko have three children.

Prince Akishino and Princess Kiko with Prince Hisahito, in Tokyo in March 2013.